1. Field of the Invention
The present invention relates generally to heat transfer in electronic units. In particular, the present invention relates to a method and apparatus for a thermally conductive packaging technique, which can be used for cooling electronic systems.
2. Description of the Related Art
Electronic components, such as tape drives, disk drives and microprocessors, operate within certain specified temperature ranges to perform efficiently. Excessive heat degrades their performances and life expectancy. The reliability of a storage device often decreases as the operational temperature increases. Such as a disk drive's data errors caused by thermal expansion and the resulting misalignment between the data transducer and the disk media. Further, higher operational temperatures also reduce the operational life of the storage device's other components. A storage device is any device that stores data. Examples of storage devices are one or more tape drives, optical devices, memory modules or disk drives.
To support advances in processors and software, the unit capacities of disk drives have increased from megabytes to gigabytes and read-write speeds have become faster. Generally, the spindle motor and actuator motor consume more power and generate more heat as speed increases. Additionally, the rotating storage disks generate more heat as the rotational speed increases. This situation results in higher operating temperatures within the drive housing. Where a single disk drive can not meet the needs of an application, multiple disk drives are employed. Therefore, hardware failures need to be minimized.
The fundamental principle behind the use of multiple disk drives in an array is that the array behaves in most respects like a single large, fast, reliable disk drive. The use of multiple drives allows the resulting storage subsystem to exceed the capacity, data integrity, and performance of the drives that make up the system, to one extent or another.
Electronic storage cabinets containing heat generating devices like disk drive arrays and servers are becoming increasingly denser, utilize high data transfer rates and need to restrict the size of apertures in the enclosures in order to attenuate radio frequency interference (RFI) and meet electromagnetic compatibility (EMC) requirements. Radio Frequency Interference is electromagnetic radiation which is emitted by electrical circuits carrying rapidly changing signals, as a by-product of their normal operation, which causes unwanted signals. Unwanted signals are interference or noise in a circuit induced by another source. These unwanted signals interrupt, obstruct, or otherwise degrade or limit the effective performance of the electronic device. Also, because of increases of clock speeds used in modern digital equipment, coupled with the lower signal levels these systems use, electromagnetic compatibility is more and more an issue.
For controlling heat in electronic devices, such as storage device arrays, typical electronic installations are historically designed for convection forced air cooling. In forced air cooling, air-moving devices draw ambient air into a housing through multiple inlet apertures strategically located to allow warm air to escape and cooler air to be drawn in. The forced air being blown through the electronic unit removes heat via convection. The typical forced air cooling of electronic units also includes channels, spaces, and gaps for the routing of the air around each of the electronic units being cooled. However, with the requirement for ever smaller electronic enclosure apertures for RFI and EMI control, effective convection cooling is increasingly difficult.
Cooling through conduction would help to eliminate the empty space, noise, airborne contamination, and vibration caused by forced air cooling. In other words, packing the disk drives densely so that conduction cooling could take place. However, the converse of this solution, for disk drives, is the problem that disk drives mounted in large arrays are susceptible to each other's rotational vibrations which can degrade the performance of adjacently mounted disk drives. Current packaging techniques try to physically isolate the drives from each other so that they are not mechanically connected. Unfortunately, this lessens the density of the array and the number of drives that may be packaged together. What is needed, currently, is a system that minimizes space, maximizes thermal transfer through conduction and, in the case of disk drives, limits vibrational transmission.